In the movement of an intermediate length of a web material such as might be found in the textile industry, the web oftentimes passes through a plurality of separate or related operations in an overall process. In each of these operations it is desirable and sometimes essential that the web be in a particular position with respect to the apparatus to ensure proper processing of the web without causing damage to the web or producing "off quality" goods. Since, as a general rule, the apparatus handling the web is substantially wider than the width of the web, lateral movement of the web across the apparatus is probable. Such lateral movement can create improper web alignment with respect to the particular equipment. Proper web alignment is particularly important in those processes where the web needs to be brought into registry to permit a normal process function. For example, in laminating, printing, tentering, and similar operations, a web must first be properly aligned prior to commencing of the process. Likewise, though not necessarily essential, good web alignment is greatly preferred for batching, coating, and virtually all web handling processes. Movement of the web out of the anticipated path of web travel may subject the web to unused and soiled parts of the web handling equipment.
Several techniques have heretofore been developed to control the lateral position of a moving web. Each of these techniques employs a device to detect the position of the web and to bring about a correction responsive thereto. Oftentimes these detectors include a beam of light that is directed across a predetermined area with a photo receiver being positioned on the opposite side of the web path. Once the web breaks the beam of light, or permits the light to be received by the photo conductor, as the system dictates, certain means are actuated to signal that the web is out of proper alignment. The web can then be manually or automatically adjusted to its proper path of travel to provide for further proper processing thereof.
One such technique which has been successful is described in U.S. Pat. No. 4,068,789 to Young et al. which is incorporated herein by reference. While the aforesaid arrangement of Young et al. has been successful, the present invention represents yet further improvement, in that, the present invention is operable for controlling various thickness webs without adjustment and imparts a very easy or soft force against the web for bringing about lateral corrective movement of the web.
The present invention thus represents an improvement in the art of such devices as will be described in complete detail hereinafter. There is no known prior art that would anticipate or suggest the method or apparatus of the present invention.